Climate and the slave trade

African societies exported more slaves in colder years. Lower temperatures reduced mortality and raised agricultural yields, lowering slave supply costs. Our results help explain African participation in the slave trade, which predicts adverse outcomes today. We use an annual panel of African temperatures and port-level slave exports to show that exports declined when local temperatures were warmer than normal. This result is strongest where African ecosystems are least resilient to climate change. Cold weather shocks at the peak of the slave trade predict lower economic activity today. We support our interpretation using the histories of Whydah, Benguela, and Mozambique.